Welding monitoring system and welding monitoring method

ABSTRACT

There are provided a welding monitoring system which can multidimensionally monitor a welding portion with high accuracy and a monitoring method thereof, by using a relatively simple configuration. 
     There is provided a welding monitoring system which monitors a subject, including: a mechanical portion; and an imaging portion, in which the mechanical portion includes a transport arm which transports the subject, a subject holding portion which holds the subject, and an energizing device which causes welding with respect to the subject to be performed, and in which the imaging portion includes imaging means for obtaining imaging data of the subject, a data recording portion which records the imaging data, an analyzing portion which extracts predetermined characteristics from the imaging data, a comparison determination portion which compares the extracted characteristics and normal characteristics to each other to determine the presence or absence of abnormality, and a determination result output portion which outputs a determination result by the comparison determination portion.

CLAIM OF PRIORITY

The present application is a divisional application of U.S. applicationSer. No. 15/786,770, filed Oct. 18, 2017, which claims priority fromJapanese Patent application serial no. 2016-205721, filed on Oct. 20,2016, the content of which is hereby incorporated by reference into thisapplication.

TECHNICAL FIELD

The present invention relates to a quality monitoring system which usesoptical means, and particularly to an efficient technology employed inquality monitoring of welded products having different sizes.

BACKGROUND ART

When managing the quality of a manufactured product by optical means,there is a case where it is necessary to capture an image not onesurface of the manufactured product but multiple surfaces thereof at thesame time. For example, in order to perform quality inspection of awelding portion in which two tubular members face each other, there is acase of imaging light emission of the entire circumference of the tubeduring the welding. In a case where such a light emitting monitoringsystem is provided on the inside of a welding machine, it is desirablethat the imaging can be performed by one camera from the viewpoint ofsaving an installation space or simplifying a system configuration.

As a background art of the field of the technology, for example, thereis a technology, such as Patent Literature 1. In Patent Literature 1, asa method for multidimensionally monitoring a subject by optical means, amethod for keeping multiple observation target surfaces in an imagingviewing field of one camera by disposing a prism on the periphery, isdisclosed.

CITATION LIST Patent Literature

PTL 1: WO 2005/083399

SUMMARY OF INVENTION Technical Problem

A case where components having different sizes exist together ascomponents which flow in a manufacturing line of a welded product whichis a subject, is considered. Even when an imaging target surface of thesubject having a certain size is focused, the subject having anothersize is generally out of focus. In other words, in the imaging target,there is a point that approaches or becomes separated from the camera,and thus, an optical path length to the camera changes nonuniformly.Therefore, only by moving the position of the camera, it is not possibleto focus on the entire imaging target region. In addition, in order toarrange the optical path lengths, when rearranging an optical system ofthe prism or the like in accordance with the size of the subject, extratime, machines, and human resources which are required for therearrangement are necessary.

Above, even in a case of monitoring the subjects having different sizes,it is desirable to configure a system that inspects the quality byimaging the subjects by automatically focusing on the entire imagingtarget region in accordance with the size.

Here, an object of the present invention is to provide a weldingmonitoring system which multidimensionally monitors a welding portionwith high accuracy and a monitoring method thereof, by using arelatively simple configuration.

Solution to Problem

In order to solve the above-described problem, according to the presentinvention, there is provided a welding monitoring system which monitorsa subject, including: a mechanical portion; and an imaging portion, inwhich the mechanical portion includes a transport arm which transportsthe subject, a subject holding portion which holds the subject, and anenergizing device which causes welding with respect to the subject to beperformed, and in which the imaging portion includes imaging means forobtaining imaging data of the subject, a data recording portion whichrecords the imaging data, an analyzing portion which extractspredetermined characteristics from the imaging data, a comparisondetermination portion which compares the extracted characteristics andnormal characteristics to each other to determine the presence orabsence of abnormality, and a determination result output portion whichoutputs a determination result by the comparison determination portion.

In addition, according to the present invention, there is provided awelding monitoring method for monitoring the subject, including: imagingthe subject during attachment and transport to a subject holdingportion; imaging the subject before welding, which is held by thesubject holding portion; imaging the subject during the welding; imagingthe subject after the welding, which is held by the subject holdingportion; imaging the subject during detachment and transport from thesubject holding portion; extracting predetermined characteristics fromeach piece of imaging data; determining the presence or absence ofabnormality by comparing the extracted characteristics and normalcharacteristics to each other; and notifying a managing system or amanager of the determined result.

Advantageous Effects of Invention

According to the present invention, by using a relatively simpleconfiguration, it is possible to realize a welding monitoring systemwhich can multidimensionally monitor a welding portion with highaccuracy, and a monitoring method thereof.

Other problems, configurations, and effects in addition to thosedescribed above will be apparent by the description of the followingembodiments.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of a welding monitoring system according to afirst embodiment of the present invention.

FIG. 2 is a view illustrating that cases where two subjects havingdifferent diameters are respectively set overlap each other, in thewelding monitoring system of FIG. 1.

FIG. 3 is a schematic view of a subject picture imaged by the weldingmonitoring system of FIG. 1.

FIG. 4 is a schematic sectional view of a welding monitoring systemaccording to a second embodiment of the present invention.

FIG. 5 is a schematic view of a welding monitoring system according to athird embodiment of the present invention.

FIG. 6 is a schematic view of a welding monitoring system according to afourth embodiment of the present invention.

FIG. 7 is a schematic view of the periphery of the subject according toa fifth embodiment of the present invention.

FIG. 8 is a schematic view illustrating an operation of a weldingmonitoring system and a flow of imaging data processing according to asixth embodiment of the present invention.

FIG. 9 is a flowchart illustrating a welding monitoring method accordingto the sixth embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an aspect (hereinafter, referred to as “embodiment”) forrealizing the present invention will be described in detail withreference to the drawings. In addition, in each of the drawings, commonparts will be given the same reference numerals, and the overlappingdescription will be omitted.

Example 1

First, a welding monitoring system according to a first embodiment ofthe present invention will be described with reference to FIG. 1. FIG. 1is a schematic view of a welding monitoring system 1 according to theembodiment.

The welding monitoring system 1 of the embodiment includes a weldingmachine 2, an imaging portion 3, a first holding portion 4, a secondholding portion 5, and four mirrors (a first mirror 8, a second mirror9, a third mirror 10, and a fourth mirror 11). The imaging portion 3includes a light receiving surface 6 for imaging a subject 20.

The welding machine 2 (not illustrated) is transported to a weldedproduct holding portion configured of the first holding portion 4 andthe second holding portion 5 by a welded product gripping arm (notillustrated). A welded product (subject 20) during the welding andbefore and after the welding is captured by the imaging portion 3, thequality is determined by analyzing the obtained image data, and theresult thereof is output to a control system of a production system oris notified with respect to a field supervisor. In addition, in FIG. 1,as a part of the configuration of the welding machine 2, the weldingmonitoring system 1 is illustrated.

Relative positions of the light receiving surface 6, the first mirror 8,and the third mirror 10 with respect to the first holding portion 4 arefixed, by a method, such as fastening. Relative positions of the secondmirror 9 and the fourth mirror 11 with respect to the second holdingportion 5 are fixed by a method, such as fastening.

A method for keeping the entire circumference of the side surface of thesubject 20 within an imaging viewing field by one light receivingsurface 6, will be described.

In order to make it easy to understand the description, as a surfacethat becomes an imaging target, a virtual square pole side surfaces thatare externally in contact with the subject 20 are considered, and one ofthe surfaces is referred to as a subject front surface 21, surfacesorthogonal to the subject front surface 21 are referred to as a subjectfirst side surface 22 and a subject second side surface 23, and asurface which opposes the subject front surface 21 is referred to as asubject rear surface 24.

The subject front surface 21 opposes the light receiving surface 6substantially to be parallel thereto, and is kept within the imagingviewing field. Hereinafter, a direction which is parallel to a normalline of the subject front surface 21 and is oriented toward the lightreceiving surface 6 from the subject front surface 21 is referred to asa first direction 25. In addition, a direction which is parallel to anormal line of the subject first side surface 22 and is oriented towardthe subject first side surface 22 from the subject second side surface23 is referred to as a second direction 26.

The first mirror 8 is installed such that the light receiving surface 6keeps the subject first side surface 22 in the viewing field. In otherwords, the first mirror 8 is installed to be substantially parallel to abisector of the first direction 25 and the second direction 26.

The second mirror 9 is installed such that the light receiving surface 6keeps the subject second side surface 23 in the viewing field. In otherwords, the second mirror 9 is installed to be substantially parallel toa bisector of a direction opposite to the first direction 25, and thesecond direction 26.

The third mirror 10 and the fourth mirror 11 are installed such that thelight receiving surface 6 keeps the subject rear surface 24 in theviewing field. In other words, the third mirror 10 is installedsubstantially to be parallel to the first mirror, and the fourth mirror11 is installed to be substantially parallel to the second mirror 9.

In FIG. 1, paths through which light to be generated on four surfacesthat surround the subject 20 reaches the light receiving surface 6 areillustrated as optical paths 27A to 27D.

The welding monitoring system 1 includes optical path length adjustmentportions 28A to 28D in front of the light receiving surface 6 on thepath through which the optical paths 27A to 27D pass. The optical pathlength adjustment portions 28A to 28D use a transparent material (forexample, glass or crystal) of which a refractive index is equal to orgreater than 1. When the light passes through the material of which therefractive index is equal to or greater than 1, by using the opticalpath length obtained by multiplying the refractive index by the lengthof the material, focusing is performed. In other words, in accordancewith the optical path to the light receiving surface 6 from each of theside surfaces of the subject 20, by adjusting the optical path lengthsof the optical path length adjustment portions 28A to 28D, the opticallengths of the optical paths 27A to 27D are arranged.

By the above-described configuration, it is possible to keep the entirecircumference of the subject in the imaging viewing field of the imagingportion 3, and to simultaneously image the entire circumference by onecamera (imaging portion 3).

Next, a method for fixing a position of the subject 20 will bedescribed. A driving mechanism is provided in the first holding portion4 or in the second holding portion 5, or in both of the first holdingportion 4 and the second holding portion 5, and the second holdingportion 5 can relatively move along the first direction 25 with respectto the first holding portion 4. By the movement, the subject 20 isinterposed and held by the first holding portion 4 and the secondholding portion 5. By the holding method, the subject front surface 21is in contact with a front surface holding surface 13 of the firstholding portion 4, and the subject rear surface 24 is in contact with arear surface holding surface 14 of the second holding portion 5.

In addition, the welding monitoring system 1 includes a load applyingmechanism 12 which applies a load to the subject 20 along the seconddirection 26. By the action of the load applying mechanism 12, when thesubject 20 is held, the subject 20 receives the load in the seconddirection 26 and is in contact with a side surface holding surface 15 ofthe first holding portion 4.

In this manner, the subject 20 is held by the first holding portion 4and the second holding portion 5, and the position thereof isdetermined.

Next, the reason why the images on four surfaces are focused even in acase of components having different sectional sizes, will be describedwith reference to FIG. 2.

By the configuration described above, the first mirror to the fourthmirror (reference numbers 8 to 11) and the optical path lengthadjustment portions 28A to 28D (not illustrated in FIG. 2) are installedto be focused in a case where the subject 20 having a certain diameter(radius r) is set. In FIG. 2, the situation is illustrated by dottedlines. Here, a case where components having different radiuses (r+Δ) areset in the welding monitoring system 1 is considered. In FIG. 2, thesituation is illustrated by solid lines. A case where the optical pathlengths of the optical paths 27A to 27D from each of the side surfaces(the subject front surface 21, the subject first side surface 22, thesubject second side surface 23, and the subject rear surface 24) of thesubject 20 to the light receiving surface 6 do not respectively change,will be described hereinafter.

First, the focus of the subject front surface 21 will be described. Thesubject front surface 21 is in contact with the first holding portion 4,and thus, there is no relative displacement with respect to the firstholding portion 4 along the first direction 25. In addition, therelative positional relationship between the light receiving surface 6and the first holding portion 4 is fixed. Therefore, even when thesectional size of the subject 20 changes, a state of being in focuswithout changing the distance between the subject front surface 21 andthe light receiving surface 6, can be held.

Next, the focus of the subject first side surface 22 will be described.The subject first side surface 22 is relatively displaced substantiallyonly by Δ with respect to the first holding portion 4 in a directionreverse to the second direction 26. In addition, the subject first sidesurface 22 is not relatively displaced with respect to the first holdingportion 4 along the second direction 26. On the optical path 27D, apoint on the subject first side surface 22 is D1, a point reflected bythe first mirror 8 is D2, and a point that has reached the lightreceiving surface is D3.

By changing the sectional size of the subject 20, the distance betweenD1 and D2 is shortened by Δ, and the distance between D2 and D3 extendsby Δ, and thus, the sum of the distance becomes exactly zero. Therefore,even when the sectional size of the subject 20 changes, it is possibleto hold a state of being in focus without changing the distance betweenthe subject first side surface 22 and the light receiving surface 6.

Next, focus on the subject second side surface 23 will be described. Thesubject second side surface 23 is relatively displaced substantially byΔ with respect to the first holding portion 4 in the direction reverseto the first direction 25. In addition, the subject second side surface23 is relatively displaced substantially by 2Δ with respect to the firstholding portion 4 in the direction reverse to the second direction 26.Furthermore, the second mirror 9 which is on the optical path 27A isrelatively displaced substantially by 2Δ with respect to the firstholding portion 4 in the direction reverse to the first direction 25.

On the optical path 27A, a point on the subject second side surface 23is A1, a point reflected by the second mirror 9 is A2, and a point thathas reached the light receiving surface is A3.

By changing the sectional size of the subject 20, the distance betweenA1 and A2 extends by Δ, the distance between A2 and A3 is shortened byΔ, and thus, the sum of the distance becomes exactly zero. Therefore,even when the sectional size of the subject 20 changes, it is possibleto hold a state of being in focus without changing the distance betweenthe subject second side surface 23 and the light receiving surface 6.

Next, focus on the subject rear surface 24 will be described. Thesubject rear surface 24 is relatively displaced substantially by 2Δ withrespect to the first holding portion 4 in the direction reverse to thefirst direction 25. In addition, the subject rear surface 24 isrelatively displaced substantially by Δ with respect to the firstholding portion 4 in the direction reverse to the second direction 26.Furthermore, the third mirror 10 which is on the optical path 27B isrelatively displaced substantially by 2Δ with respect to the firstholding portion 4 in the direction reverse to the first direction 25.

On the optical path 27B, a point on the subject rear surface 24 is B1, apoint reflected by the third mirror 10 is B2, a point reflected by thefourth mirror 11 is B3, and a point that has reached the light receivingsurface is B4.

By changing the sectional size of the subject 20, the distance betweenB1 and B2 extends by Δ, the distance between B2 and B3 is shortened by4Δ, the distance between B3 and B4 extends by 3Δ, and thus, the sum ofthe distance becomes exactly zero. Therefore, even when the sectionalsize of the subject 20 changes, it is possible to hold a state of beingin focus without changing the distance between the subject rear surface24 and the light receiving surface 6.

A picture in a process from the setting of the subject 20 in the subjectholding portion to the welding is illustrated in FIG. 3. The process isarranged in a time-series order from top (T1) to bottom (T4) of FIG. 3,and in T1, in a state where the subject 20 is not set, only the mirrors(reference numbers 8, 9, and 11) are kept within the imaging viewingfield. In addition, before the subject 20 is set, the first holdingportion 4 and the second holding portion 5 are separated from eachother, and thus, compared to the first mirror 8 fixed to the firstholding portion 4, the second mirror 9 and the fourth mirror 11 whichare fixed to the second holding portion 5 are projected to be small.

In T2, a picture in the middle of movement of the subject 20 by atransport arm toward the right side from the left side on a papersurface of FIG. 2 is illustrated. An arrow illustrated in T2 illustratesa moving direction of the subject 20. In addition, a symbol Xillustrates a direction toward the near side from the far side on thepaper surface.

In T3, a state where the movement of the transport arm is finished isillustrated. T4 illustrates a state after the second holding portion 5relatively moves with respect to the first holding portion 4, and holdsthe subject 20. As the second mirror 9 and the fourth mirror 11 approachthe first holding portion 4, the entire side surface of the subject 20enters the imaging viewing field, and the preparation of imaging duringthe welding is completed. After the welding, the picture to bereproduced is recorded from T4 to T1 in reverse.

Action and Effect

In this manner, in the welding monitoring system 1 according to thefirst embodiment, the mirror for keeping the entire circumference of thesubject within the viewing field of the light receiving surface canautomatically perform the focusing by moving in accordance with thesectional size of the subject 20. In other words, by cancelling thedisplacement of the optical path caused by the change in subject size bythe displacement of the subject holding portion, the entirecircumference of the subject can be focused.

Example 2

A welding monitoring system according to a second embodiment of thepresent invention will be described with reference to FIG. 4. FIG. 4 isa schematic view of the welding monitoring system 1 according to theembodiment.

The welding monitoring system 1 according to the embodiment is differentfrom the configuration of the welding monitoring system 1 according tothe first embodiment in the configuration of the optical path lengthadjustment portion 28. Since other configurations of the weldingmonitoring system 1 according to the embodiment are the same as those ofthe welding monitoring system 1 according to the first embodiment, thedescription thereof will be omitted.

In the welding monitoring system 1 according to embodiment, an opticalpath length adjustment portion 7 includes a plurality of optical pathlength extending mirrors 29 instead of the transparent material of whichthe refractive index is equal to or greater than 1. Without changing astart point (subject 20) of the optical paths 27A to 27D, each of thereflection points by the first mirror 8 to the fourth mirror 11, and afinal point (light receiving surface 6), the optical path lengthextending mirror 29 is installed to make the optical path lengthsuniform by extending the optical path lengths by bending the middle partof the path. Accordingly, a function of making the optical path lengthsof optical paths 27 uniform can be realized by bending the optical pathnot only in a linear space between the imaging target part and the lightreceiving surface 6 but also in the direction perpendicular thereto, andthe installation space can be more efficiently used.

Action and Effect

In this manner, in the welding monitoring system 1 according to thesecond embodiment, not only the effects similar to those of the weldingmonitoring system according to the first embodiment can be obtained, butalso it is possible to more efficiently use the installation space ofthe configuration member of the welding monitoring system 1 byconfiguring the optical path length adjustment portion 7 by theplurality of optical path length extending mirrors 29.

Example 3

A welding monitoring system according to a third embodiment of thepresent invention will be described with reference to FIG. 5. FIG. 5 isa schematic view of the welding monitoring system 1 according to theembodiment.

The welding monitoring system 1 according to the embodiment is differentfrom the configuration of the welding monitoring system 1 according tothe first embodiment in that the second holding portion 5 also functionsas the load applying mechanism 12. Since other configurations of thewelding monitoring system 1 according to the embodiment are the same asthose of the welding monitoring system 1 according to the firstembodiment, the description thereof will be omitted.

In the welding monitoring system 1 according to the embodiment, theapplying of the load in the second direction 26 of the subject 20 whichis an action of the load applying mechanism 12 is realized by theconfiguration of the rear surface holding surface 14 of the secondholding portion 5. The rear surface holding surface 14 is not parallelto the front surface holding surface 13 of the first holding portion 4,and a normal line thereof is configured to have not only the componentof the first direction 25 but also the component of the second direction26.

Accordingly, as the second holding portion 5 moves toward the firstdirection 25 with respect to the first holding portion 4 and comes intocontact with the subject 20, it is possible to apply the load in thesecond direction 26 to the subject 20. By the above-describedconfiguration, even when eliminating the load applying mechanism 12which is provided in the welding monitoring system 1 according to thefirst embodiment, it is possible to obtain similar effects.

Action and Effect

In this manner, in the welding monitoring system 1 according to thethird embodiment, not only the effects similar to those of the weldingmonitoring system according to the first embodiment can be obtained, butalso it is possible to eliminate the configuration member of the weldingmonitoring system 1 by the configuration in which the second holdingportion 5 also plays a role of the load applying mechanism 12.

Example 4

A welding monitoring system according to a fourth embodiment of thepresent invention will be described with reference to FIG. 6. FIG. 6 isa schematic view of the welding monitoring system 1 according to theembodiment.

The welding monitoring system 1 according to the embodiment is differentfrom the configuration of the welding monitoring system 1 according tothe first embodiment in that a magnifying lens 30 and a condensingmirror 31 are provided in front of the light receiving surface 6. Sinceother configurations of the welding monitoring system 1 according to theembodiment are the same as those of the welding monitoring system 1according to the first embodiment, the description thereof will beomitted.

In the welding monitoring system 1 according to the embodiment, in frontof the light receiving surface 6 in the middle of the optical paths 27Ato 27D, the magnifying lens 30 and the condensing mirror 31 areinstalled. Accordingly, the light generated from each of the sidesurfaces (the subject front surface 21, the subject first side surface22, the subject second side surface 23, and the subject rear surface 24)of the subject 20 is condensed to be densely focused on the lightreceiving surface 6. By the above-described configuration, it ispossible to perform the imaging by improving resolution of the subject20.

Action and Effect

In this manner, in the welding monitoring system 1 according to thefourth embodiment, not only the effects similar to those of the weldingmonitoring system 1 according to the first embodiment can be obtained,but also it is possible to perform the imaging by improving theresolution of the subject 20 by providing the magnifying lens 30 and thecondensing mirror 31 of the light receiving surface 6.

Example 5

A welding monitoring system according to a fifth embodiment of thepresent invention will be described with reference to FIG. 7. FIG. 7 isa schematic view of the periphery of the subject 20 according to theembodiment.

The welding monitoring system 1 according to the embodiment is differentfrom the configuration of the welding monitoring system 1 according tothe first embodiment in that a slit 32 is installed on the periphery ofthe subject 20. Since other configurations of the welding monitoringsystem 1 according to the embodiment are the same as those of thewelding monitoring system 1 according to the first embodiment, thedescription thereof will be omitted.

In the welding monitoring system 1 according to the embodiment, aplurality of the radial slits 32 around the subject 20 are provided onthe periphery of the subject 20. By the slit 32, it is possible toperform the imaging by extracting a ray of light which is substantiallyperpendicular to a curved surface (surface of the subject 20) from thegenerated light of the subject 20. Therefore, it is possible to narrow apoint on the subject 20 which is a starting point of the ray of lightthat has reached each point on the light receiving surface 6, and tosuppress widening (blur) of the image.

Action and Effect

In this manner, in the welding monitoring system 1 according to thefifth embodiment, not only the effects similar to those of the weldingmonitoring system 1 according to the first embodiment can be obtained,but also it is possible to suppress blur during the imaging by providingthe slit 32 on the periphery of the subject 20.

Example 6

A welding monitoring system and a welding monitoring method according toa sixth embodiment of the present invention will be described withreference to FIGS. 8 and 9. FIG. 8 is a schematic view of a systemconfiguration of the welding monitoring system 1 according to theembodiment. FIG. 9 is a flowchart illustrating a welding monitoringmethod according to the embodiment.

The embodiment is different from the configuration of the weldingmonitoring system 1 according to the first embodiment in that a seriesof information processing and control systems is provided. Since otherconfigurations of the welding monitoring system 1 according to theembodiment are the same as those of the welding monitoring system 1according to the first embodiment, the description thereof will beomitted.

The welding monitoring system 1 according to the embodiment isconfigured of the mechanical portion which transports the subject 20 forthe welding at a predetermined position, and the imaging portion whichdetermines the quality by imaging the subject 20 and analyzing the imagedata. The mechanical portion includes, for example, the transport arm,the subject holding portion, and the energizing device. The imagingportion includes, for example, a data recording portion, an analyzingportion, a comparison determination portion, and a determination resultdisplay portion (determination result output portion).

The imaging portion images a subject in each process of the operation ofthe mechanical portion. Specifically, for example, the imaging isperformed in a process in which the transport arm transports the subjectto the subject holding portion (imaging 1), a subject after the holdingby the subject holding portion (imaging 2), a process of operating theenergizing device and performing the welding (imaging 3), a subjectafter the welding (imaging 4), and a process in which the subject istransported by the transport arm again for performing the process afterthe welding (imaging 5).

The imaging data of the subject 20 obtained in this manner istransported to the data recording portion, and characteristics which arerequired in determination of the quality in the analyzing portion areextracted. The analysis result is input to the comparison determinationportion, and is recorded in an analysis result accumulation portion. Inthe comparison determination portion, for example, compared to theprevious data recorded in the analysis result accumulation portion orsubject shape data, the presence or absence of abnormality is output.The abnormality is notified with respect to a field supervisor byabnormality informing means, and is informed with respect to amanufacturing execution system (MES) which controls the entireproduction system or a portable terminal via a programmable logiccontroller (PLC), and thus, necessary controls are performed.

A specific example of abnormality to be sensed will be described. Fromthe picture of the process in which the transport arm transports thesubject to the subject holding portion (imaging 1), it is possible toinvestigate necessity of maintenance of a driving portion of the arm bycalculating an operation speed of the transport arm and by sensing thepresence or absence of the abnormality of the arm. From the picture ofthe subject (imaging 2) after the holding performed by the subjectholding portion, it is possible to sense whether or not the subject isheld at a predetermined position, and to investigate whether or not thewelding is performed at a predetermined positional relationship. Fromthe picture of the process of operating the energizing device andperforming the welding (imaging 3), it is possible to investigate thepossibility of a welding defect by analyzing the light generation of thesubject. From the picture of the subject after the welding (imaging 4),it is possible to sense the presence or absence of damage or dirt of thesubject, and to investigate whether or not the predetermined quality ofexternal appearance is satisfied. From the picture of the process ofoperating the transport arm again for performing the process after thewelding (imaging 5), it is possible to investigate the presence orabsence of abnormality of the arm again.

The welding monitoring method of the embodiment described above isillustrated in the flowchart of FIG. 9. First, the subject (weldingmember) is transported to the subject holding portion by the transportarm (step S1). The subject (welding member) during the transport iscaptured, and the imaging data is recorded in the data recording portion(step S2).

Next, the subject (welding member) is fixed and held to the subjectholding portion by the load applying mechanism (step S3). In a statewhere the subject (welding member) is held by the subject holdingportion, the subject (welding member) before the welding is captured,and the imaging data is recorded in the data recording portion (stepS4).

Then, the subject (welding member) is welded by the energizing device(welding machine) (step S5). The subject (welding member) during thewelding is captured, and the imaging data is recorded in the datarecording portion (step S6). Furthermore, in a state where the subject(welding member) is held by the subject holding portion, the subject(welding member) after the welding is captured, and the imaging data isrecorded in the data recording portion (step S7).

Then, the subject (welding member) after the welding is carried out bythe transport arm (step S8). The subject (welding member) during thetransport is captured, the imaging data is recorded in the datarecording portion (step S9).

Then, the predetermined characteristics are extracted from the imagingdata obtained in each of the steps (step S10).

After this, normal characteristics are read from a subject shape database (step S11). The predetermined characteristics of the imaging dataextracted in step S10 and the normal characteristics of the subject readin step S11 are compared to each other, and the presence or absence ofabnormality is determined (step S12). In a case where it is determinedthat the abnormality is absent, the process moves to step S13, thecontent that the state is normal is notified with respect to themanaging system or the manager, and the operation of the welding machinecontinues. Meanwhile, in a case where it is determined that theabnormality is present, generation of the abnormality is notified withrespect to the managing system or the manager (step S14).

Action and Effect

In this manner, in the welding monitoring system 1 according to thesixth embodiment, not only the effects similar to those of the weldingmonitoring system 1 according to the first embodiment can be obtained,but also it is possible to sense the abnormality in the welding process,and to control the operation situation of a production line, byanalyzing the image data obtained by the imaging portion.

In addition, the present invention is not limited to the above-describedexamples, and various modification examples are included. For example,the above-described examples are described in detail for making it easyto understand the present invention, and are not limited to the examplein which all of the described configurations are necessarily provided.In addition, it is possible to replace apart of the configuration of acertain example with a configuration of other examples, and it is alsopossible to add a configuration of other examples to the configurationof a certain configuration. In addition, it is possible to add,eliminate, and replace other configurations with respect to a part ofthe configuration of each of the examples.

REFERENCE SIGNS LIST

-   1 . . . WELDING MONITORING SYSTEM-   2 . . . WELDING MACHINE-   3 . . . IMAGING PORTION-   4 . . . FIRST HOLDING PORTION-   5 . . . SECOND HOLDING PORTION-   6 . . . LIGHT RECEIVING SURFACE-   7 . . . OPTICAL PATH LENGTH ADJUSTMENT PORTION-   8 . . . FIRST MIRROR-   9 . . . SECOND MIRROR-   10 . . . THIRD MIRROR-   11 . . . FOURTH MIRROR-   12 . . . LOAD APPLYING MECHANISM-   13 . . . FRONT SURFACE HOLDING SURFACE-   14 . . . REAR SURFACE HOLDING SURFACE-   15 . . . SIDE SURFACE HOLDING SURFACE-   20 . . . SUBJECT-   21 . . . SUBJECT FRONT SURFACE-   22 . . . SUBJECT FIRST SIDE SURFACE-   23 . . . SUBJECT SECOND SIDE SURFACE-   24 . . . SUBJECT REAR SURFACE-   25 . . . FIRST DIRECTION-   26 . . . SECOND DIRECTION-   27, 27A, 27B, 27C, 27D . . . OPTICAL PATH-   28, 28A, 28B, 28C, 28D . . . OPTICAL PATH LENGTH ADJUSTMENT PORTION-   29 . . . OPTICAL PATH LENGTH EXTENDING MIRROR-   30 . . . MAGNIFYING LENS-   31 . . . CONDENSING MIRROR-   32 . . . SLIT

The invention claimed is:
 1. A welding monitoring method for monitoringa subject, comprising: imaging the subject before, during, and afterwelding, wherein before welding the subject is transported and attachedto a subject holder comprising a first support and a second supportconfigured to hold the welding subject in place during imaging, andwherein after welding the subject is detached and transported from thesubject holder, wherein the imaging is performed by a camera including alight receiving surface to which a relative position with respect to thefirst support is fixed during imaging, a first mirror to which therelative position with respect to the first support is fixed duringimaging, and a second mirror to which a relative position with respectto the second support is fixed during imaging, and wherein the firstmirror and the second mirror are disposed such that the subject remainsin an imaging viewing field of the camera during imaging, wherein thesecond support moves the subject toward a position determined in advancein the first support, and images the subject in a state where thesubject is in contact with both of the first support and the secondsupport during imaging, and wherein the imaging comprises adjusting anoptical path using an optical path length adjustment portion forfocusing, the optical path length adjustment portion being configured ofthe first and second mirrors on an optical path to the light receivingsurface from the subject, the optical path length adjustment portionbeing formed of transparent material having a refractive index is equalto or greater than 1; extracting predetermined characteristics from eachpiece of imaging data; determining the presence or absence ofabnormality by comparing the extracted characteristics and normalcharacteristics to each other; and notifying a managing system or amanager of the determined result.
 2. The welding monitoring method ofclaim 1, further comprising transporting the subject to and from thesubject holder by a transport arm.
 3. The welding monitoring method ofclaim 1, wherein adjusting the length of the optical path focuses lightbetween the light receiving surface and the subject.
 4. The weldingmonitoring method of claim 1, wherein adjusting the length of theoptical path includes extending the length of the optical path bybending the optical path.